Is my PC underpowered?

Ok on to my question, I have this feeling my PC is underpowered, don't know why, but I really think so.

My specs are:

I5 750

P55 WB mobo

GTX285 Sparkle 1gig

4 gig ram

TB hard drive

550 watt Huntkey Titan power supply.

I have a sneaky feeling my 285 is underpowered, I originally wanted to get a 700 + PSU though the guy at the shop was 100% sure that the 550 would be enough. I was low on money so I trusted him. Though my pc is really warm imo, 35 C idle and upto 60 C doing some intensive gaming. Fair enough this was summer, now in winter it's a lot better. I have 6 fans in total nl. CPU, Graphics card. PSU, Front bottom, side middel, back top. Also it doesn't exactly perform as I hoped it would.

I basicly get the sam frame rates as guys with 3.0 ghz duals, and GTX 260, 2gig ram. I do get more than he does and some other friends but still, I would expect more than I'm getting. In graphics intense games I would get 70 - 90(BFBC2) and he would get(50 - 80). Though I usually get 60 with Vsync to match my Montior Hz. Modern Warfare I get (90 - 350(looking at a wall)) and he gets (80 - 300). I don't think this is much of a difference, though I might be wrong.